Earth’s sulfur cycle is more varied and has greater effects on marine chemistry, the carbon cycle, atmospheric oxygen levels, and climate than previously realized, according to two reports in Science (DOI: 10.1126/science.1220656 and 10.1126/science.1220224). Sulfate from dissolved minerals such as an­hydrite (CaSO4) or from oxidative weathering of pyrite (FeS2) gets carried by rivers into . . .